Grinding device



April 12, 1938. I WGEVEKE 2,114,106

GRINDING DEVICE Filed Aug. 11, 1936 uliwl a z L g} Fig.2.

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Patented Apr. 12, 1938 UNITED STATES PATENT OFFICE Application August 11, 1936, Serial No. 95,369

In the Netherlands August 20, 1935 v 3 Claims.

This invention relates to a device for grinding knives and scissors and of the kind comprising a pair of grinding wheels which are mounted on a driving element so as to be capable of axial displacement and which are clamped by spring pressure together and to an interposed piece of work.

In known devices of this kind the grinding wheels, while being axially displaceable on the driving element in opposition to the springs, are positively rotated by said element, so that the speed of the wheels will not be effected by the pressure thereon of the work. This leads to uneven grinding, overheating, and spoiling of the work.

The object of the present invention is to ensure uniform and regular grinding, and the invention consists essentially in coupling the grinding wheels to the driving element by the mere pressure exerted by the spring or springs against the wheels and against the abutments on the driving element. By this arrangement excessive pressure of the work against the wheels will cause the latter to slip relative to the driving element, so that overheating and irregular grinding will be obviated.

. As a further means for preventing irregular grinding, the grinding wheels are mounted on a driving element which is positively rotated by a shaft but which is capable of axial displacement thereon, so that the grinding wheels can move axially within narrow limits and adjust themselves to the work independently of the springs.

Fig. 1 of the accompanying drawing represents a longitudinal section of a grinding device con structed according to the invention,

Fig. 2 is an end view of the device without the driving motor, and

Fig. 3 is a plan view thereof.

The device comprises an electric motor a on the shaft b of which a sleeve 1 is loosely mounted. The sleeve has a. hollow head 9 within which a collar 0 on the shaft is accommodated, and a setscrew d, which fixes the collar to the shaft, passes through an elongated, longitudinal slot 1 in the head 9, so that the sleeve will be positively rotated by the shaft while it is free to move on the shaft in axial direction as far as allowed by the slot 1. Loosely mounted in juxtaposition on the sleeve y are two grinding wheels h andis each of which has the form of a cylindrical ring. Two coil springs l and m are arranged on the sleeve at opposite sides of the grinding wheels for clamping the latter together. For this purpose the spring Z bears at one end against the head 9, and the spring m bears against a washer n which is secured to the sleeve 11 through the medium of a cross-pin o. Arranged in this manner, the grinding wheels, which are loosely slipped on to the sleeve, will only be frictionally coupled to the drive. Under strong pressure of the work the 5 wheels will be able to yield in opposition to the springs and to slip on the sleeve so as to ensure uniform movement.

The grinding wheels are provided with convex side faces by which they bear against each other and owing to which a circumferential groove is formed between the wheels wherein a knife edge may be ground at both sides simultaneously. For guiding the work when grinding knives and scissors, for collecting the dust, and as a guard against flying fragments in case the wheels should break, a drum r is provided which envelopes the grinding elements and which is secured by means of a screw it to a flange 2 on the motor casing. The drum, which is readily de- 20 tachable for cleaning, occupies an eccentric position relative to the motor shaft, the upper wall portion thereof being in close proximity to the grinding wheels. In this wall portion a slot s is made through which knives may be introduced into the groove between the wheels for grinding. The slot is elongated so as to form a guide for the knife and occupies an oblique position relative to the groove, as shown in Fig. 3, so that the knives will move through the groove at an angle thereto and be ground at both sides of the edge. Since the sleeve 1; is capable of axial displacement on the shaft b, the wheels will adjust themselves to the knives, so that the latter will always be uniformly ground on both sides whether they are held steadily or not.

The grinding of scissors is effected by moving the edge of each blade against the side face of the outer grinding wheel. For this purpose the drum r is made with an oblique opening in which there is an inclined guide plate 11. for the scissor blades. The plate is hinged at t to the drum and movable about an axis which is substantially parallel to the oblique slot s, and it is supported on an eccentric disc 12 which is rotatably mounted on the end wall of the drum and which can be turned for adjusting the inclination of the plate. The adjustment is effected by means of a lever arm w which is squared on a screw bolt e that holds the disc and serves as a pivot therefor. A wing nut i on the bolt e allows the arm and disc to be secured in adjusted position to the end wall of the drum which is provided with graduations indicating, with reference to the arm, the angle at which the scissors are being ground. Also in this case uniformity of grinding is ensured by, the resilient mounting of the grinding wheels which will slip under excessive pressure.

Instead of the two coil springs l and m a single spring may be used arranged to clamp the wheels against the washer n.

The grinding wheels h and k, which are symmetrical in shape, can be interchanged and reversed for the renewal of the operative grinding faces.

I claim:

1. A device for grinding knives and scissors comprising a pair of grinding wheels in the form of cylindrical rings, a rotary supporting and driving element whereon said wheels are loosely mounted in juxtaposition, spring means for clamping the wheels together and coupling them frictionally to the driving element, each wheel being formed with convex side faces adapted to form a circumferential grinding groove between the abutting wheels, a dust collecting drum surrounding the wheels and the driving element, said drum being eccentric relative to the wheels and formed with oblique slots, one for admitting the work to the grinding groove between the wheels and another for admitting the work to the side face of the outer wheel, a guide plate for the work supported on the drum in said latter slot, and means for regulating the angular position of said plate.

2. A device as claimed in claim 1 wherein the means for adjusting the guide plate comprises an eccentric plate supporting disc mounted on the drum, and a lever for adjusting said disc.

3. A device for grinding knives and scissors comprising a pair 01 grinding wheels, a rotary supporting and driving element whereon said wheels are loosely mounted in juxtaposition, spring means operative to clamp the grinding wheels together and couple them frictionally to the driving element, a dust collector and guard comprising a drum surrounding the grinding wheels and the driving element, said drum being eccentric relative to the wheels and formed with oblique slots admitting the work to the wheels, and an adjustable guide plate for the work supported on the drum in one of said slots.

WILLIAM GEVEKE. 

